Tohoros 4:10

Rabbi Yosi says that a case of doubt regarding liquids is ruled unclean vis-à-vis food and clean vis-à-vis utensils, as follows: Let’s say that there were two jars, one ritually unclean and one ritually clean. If a person made dough with the contents of one jar and a doubt arose as to whether it was made with the contents of the unclean jar or the clean jar, this is a case of doubt regarding liquids in which food is ruled unclean and utensils are ruled clean.

Tohoros 4:11

“A doubt regarding whether hands have been rendered unclean, conveyed impurity or been purified is ruled clean,” “a doubt that arose in a public domain,” “a doubt regarding rabbinic law” (all from mishna 4:7) – for example, doubts as to whether one ate ritually-unclean food or drank ritually-unclean liquids, whether one immersed his head and the major part of his body in drawn water, or whether three log of drawn water fell on a person’s head and the major part of his body – all such cases of doubt are ruled clean. However, if a case of doubt arose regarding a primary source of impurity (av hatumah) it is ruled unclean even if it’s only an av hatumah under rabbinic law.